Garden Railway Forum

I'm wondering if the metallurgist brethren out there can advise me. I want to make a jig for bending the loops for my LGB replacement couplings but am struggling. My usual approach of driving brass nails into a piece of plywood isn't really up to the job. The problem is that the 1.5mm brass rod is quite difficult to bend around the nails - the distances between the nails are only 15mm. As you can see, I'm struggling to get the bends consistent. Is there something I can do to aid the bending process - or can anyone suggest a more effective design of jig (which would be within my capabilities as a kitchen-table modeller)?

Rik

Would heating the wire up first and then using a single upright nail in a vice to bend around be better?

I've never found brass rod easy to bend, but I've never tried heating them as suggested by Tom. My method for brass rod has been to file part way through into a V, bend to shape and then strengthen the bend with a fillet of solder.

Alternatively I've used steel spring wire which, both bends easier and is strong. I got my steel spring wire from Eileens Emporium.

Ian

tom_tom_go wrote: ↑Wed May 16, 2018 2:12 pm Would heating the wire up first and then using a single upright nail in a vice to bend around be better?

I'll try a bit of heat and see what happens.

It's not the actual bending which is the problem. I can easily do it with pliers, but it's trying to get the bends in the right place and to the correct angle which is the problem. The jig is my attempt to get all the bends in the right places. The jig would be OK with finer gauge rod, but not with this heavier gauge stuff.

Rik

Rik

ge_rik wrote: ↑Wed May 16, 2018 5:46 pm
I'll try a bit of heat and see what happens.

I hesitated to suggest heating it, because without fairly sophisticated temperature control, you risk not heating enough and achieving nothing or over heating and completely softening it and making it useless for what you want. I guess you could then try hardening it subsequently, but thats adding all sorts of complication on top.

Rather than 1.5mm rod, have you considered using small rectangular section strip on edge, say something like 1 x 2mm, which would bend more easily and still be small enough to accept the hook?

Would the jig work better with a solid block to bend around I.e. a flat shape the size of the inside of the coupling. It would need to be something solid and assuming metal is out 2mm plasticard?

ge_rik wrote: ↑Wed May 16, 2018 1:51 pm I'm wondering if the metallurgist brethren out there can advise me. I want to make a jig for bending the loops for my LGB replacement couplings but am struggling. My usual approach of driving brass nails into a piece of plywood isn't really up to the job. The problem is that the 1.5mm brass rod is quite difficult to bend around the nails - the distances between the nails are only 15mm.
IMG_7576.JPG

As you can see, I'm struggling to get the bends consistent.
IMG_7577.JPG

Is there something I can do to aid the bending process - or can anyone suggest a more effective design of jig (which would be within my capabilities as a kitchen-table modeller)?

Rik

Hi Rik,

The jig looks out to me. The nail on the left is outside of the top left hand one.

Do you bend the wire first with the two little ends, or bend it in one go.

I would bend the wire straight, doing it with two bends, then turn it over and do the other two. You would need to put two more nails the same width of the wire at the top of the jig, so the wire will stay firmly in place while you bend the 1st one.

Then turn the wire up and over the 2nd nail to the right ( I am right handed ) and do the 2nd bend. The 1st two bends would lie against the other two nails. Also the tops of the nails would need to be removed, so you can slide the wire over and off the jig when done.

Then bend and cut the ends to the required length.

It is pretty much how I used to bend exhaust pipes on a CNC pipe bender for a company I used to work for using X,W,Z configurations.

Hope this is helpful Rik. It should work better with a little practice….

philipy wrote: ↑Wed May 16, 2018 8:33 pm Rather than 1.5mm rod, have you considered using small rectangular section strip on edge, say something like 1 x 2mm, which would bend more easily and still be small enough to accept the hook?

With a tongue only partly in cheek, I'd try taking hammer and bashing the round rod into a flat and see if it bent any easier.

gregh wrote: ↑Thu May 17, 2018 10:37 am

philipy wrote: ↑Wed May 16, 2018 8:33 pm Rather than 1.5mm rod, have you considered using small rectangular section strip on edge, say something like 1 x 2mm, which would bend more easily and still be small enough to accept the hook?

With a tongue only partly in cheek, I'd try taking hammer and bashing the round rod into a flat and see if it bent any easier.

I've done that in the past, but the trouble is that it work hardens from the hammering and then cracks on the bends.

I have just drawn this design but not tested it myself..... With a block of wood screwed firmly behind the outer nails it should prevent any curvature and allow equal bends to be made. You will need to cut off nail heads to enable removal from the jig.
Might be worth a try?

ge_rik wrote: ↑Wed May 16, 2018 1:51 pm Is there something I can do to aid the bending process - or can anyone suggest a more effective design of jig (which would be within my capabilities as a kitchen-table modeller)?

No Metallurgists here in Aust., they re-invented themselves as Materials Engineers years ago. I worked with them for most of my career and some of it rubbed off...........

Heating the 1.5mm rod won't make much difference to how easily it bends unless you take it up to red heat, which will anneal it. At which point it will have the mechanical properties of soggy spaghetti......

The metallurgical issue is that the wire is work hardened when it is drawn to size and only partly annealed afterwards, so it is a bit springy. When you bend it, it tends to bend back a bit when released (referred to as springback by metallurgists). It has to be bent past the nominal angle, so it will spring back to the correct angle. With a fixed pin jig like yours the other pins prevent the wire being bent far enough to get the correct final angle.

So......

1. The jig needs to have removable pins, so it works the same way as a jewellers wire forming jig.

2. The wire needs to be pushed with a flat block so it only bends where it passes around a pin. The block should be metal for preference, but hardwood will work.

The way bending coupler loops in a jig with removable pins would work is as follows -

- Bend the short locating arm at one end with pliers and push into the hole in the jig.

- Fit the first pin into the jig and using a couple of blocks to keep things straight, put in the first bend, pushing far enough that the wire comes back to the edge of the second pin hole.

- Fit the second pin and make the next bend using the two blocks to keep things straight until the wire lines up with the edge of the third pin hole.

- repeat with the other two pins until the coupler loop is formed.

- To form the last locating leg, you will need a right angle cut in the corner of the jig, so the wire can be pushed down to form the last angle.

- Remove the pins, then remove the coupler loop and start all over again.

-You may need to clamp the wire down as you go, so it doesn't twist as it is formed.


Being me, I'd make the jig in metal and have screw in pins. I've not made anything like it in wood, but I'd make the following observations for a kitchen table job......

Make the pins out of steel nails and use a thick block of hardwood. The holes for the nails need to be deep and a sliding fit on the nails, so the nails will be well supported against side load. Using a softwood like pine would be unlikely to last long enough to do the number of loops you need to make, as the holes will slowly get enlarged, allowing the pins to move out of line.

Wood is a pig of a material to drill accurately for making jigs, especially with a hand drill. If you can find a suitable size block of a dense plastic like Tufnol, it would work better for making a jig.


I hope that all makes sense.

Regards,
Graeme

Thanks folks
I've redone the jig and it's now a bit more uniform. I've discovered that over-bending a little and then bending back helps to tighten the bends. I've also removed the heads of the nails and shortened them, which helps a lot.

Basically, the jig helps ensure that the bends are in the right places. When I remove the wire from the jig, I then do a bit of tweaking with pliers to tidy up the geometry of the angles.

I'm set to make 134 couplings (at the last count). I'd forgotten that I have four sets of tipplers which are permanently coupled into rakes of 4 and so won't need intermediate couplings (just couplings at the ends), so not quite the 150 I was anticipating. As the new couplings are compatible with the old, I can take my time over replacing them - well that's the plan anyway.

Rik

Thats a good plan Rik. Glad you have got something sorted with the bending issue. There are lots of differing ways of doing it. But you seem to have found your way with it. Its something only you can do yourself after trying various other ways. But in the end it’s what is comfortable and easy for you.

134 to do, or is that now 133…..

What is the finished item supposed to look like? Maybe there are other ways to make the parts and perhaps from a different material.

Busted Bricks wrote: ↑Fri May 18, 2018 2:26 pm What is the finished item supposed to look like? Maybe there are other ways to make the parts and perhaps from a different material.

I'm wanting to replace LGB couplings with something less obtrusive but retain compatibility with LGB. Brass wire seems like a fairly good way to achieve that.

Rik

Another topic full of really useful information
In particular, Graeme's post is worthy of being added to the reference library. There are other posts which should be put there too - it can be a real b*gger finding the post you want to refer to sometimes, when doing something you've previously seen explained!

I agree about having a reference thread on this subject, but I think it should be an open thread that members can see which is most suitable for them and also for other members to add anything that would make the job easier.

There are loads of different ways that one could make a jig, it alls depends on what and how you do it.

You can bookmark this thread so you can refer to it.